My 4 year old son always asks to see the flightdeck when we leave the aircraft, these are normally Swiss flights and the Captain is generally standing by the door (maybe company policy ?) and he's never been refused, most times they wait until everyone else has disembarked though. They normally let him sit in one of the seats as well, though they get a bit concerned when he goes for some of the switches
Both CC and FC seem to be extremely tolerant of children in general, in fact I'd go as far to say that a lot of them have the patience of saints. I'm assuming this is covered somewhere in your training, please tell us these secrets !!